(1) Field of the Invention
The present invention relates to a fastener system for fastening a load to a rotorcraft, and to a rotorcraft provided with the fastener system. The invention also relates to a method of implementing the system.
The technical field of the invention is thus that of devices for fastening an external load to an aircraft, and in particular to an aircraft having a rotary wing.
(2) Description of Related Art
Conventionally, a rotorcraft has a fuselage carrying at least one rotor for providing lift, and possibly also propulsion. The rotorcraft may then be provided with a releasable fastener system for carrying an external load.
Such a fastener system may usually include attachment means. Such attachment means may comprise a release hook that is fastened to the fuselage and optionally swivel-mounted. A sling is then attached to the release hook for the purpose of enabling external loads to be carried.
The attachment means are advantageously positioned under the fuselage close to a point in alignment with the lift rotor for centering purposes. Nevertheless, the rotorcraft might not have any structural element suitable for carrying the attachment means in such a zone.
Under such circumstances, the fastener system may include a support beam for carrying the attachment means. The support beam is then fastened to structural elements of the rotorcraft.
Such a support beam may comprise two vertical section members connected together by a horizontal core. The release hook is housed in a housing defined by the vertical section members and the horizontal core. More precisely, the release hook may extend in the same direction as the vertical section members extend, or it may extend in a direction orthogonal to that direction.
Such a fastener system is in satisfactory use in the field of aviation.
Nevertheless, the support beam may be found to be aggressive in the event of the rotorcraft crashing.
The structure of the beam is relatively indeformable and it runs the risk of penetrating into the fuselage under the effect of reaction from the ground.
The situation is made more complicated when the rotorcraft has fuel tanks in the bottom portion of its fuselage that is supporting the support beam.
In the bottom zone of the fuselage, the rotorcraft then includes in particular a plate that serves to receive pumps, gauges, and other pieces of equipment of the fuel circuit, for example. The plate is designed to withstand contact with the ground in the event of a crash and thus to prevent the tank from leaking. Nevertheless, an impact against the support beam can be destructive.
The technological background remote from the invention includes the following documents: U.S. Pat. No. 5,190,250, DE 196 23 562, U.S. Pat. No. 4,637,575, and U.S. Pat. No. 6,059,266.